SQL 查询以获取时间戳列中没有小时数的数据

Question

我已经编写了代码和 sql 查询以从数据库中获取数据：

sql_tables <- glue("
SELECT *
FROM mytable
LIMIT 4
")
table <- dbGetQuery(con, stri_encode(sql_tables, to = "UTF-8")) %>%
     as.data.frame()

我得到这个数据框：

ID      value                    timestamp
1       message sent      2019-05-29 06:45:34
2       sold out          2019-05-29 07:55:29
3       processed         2019-05-30 17:42:11
4       processed         2019-05-30 19:44:15

我想编写另一个查询以仅获取 2019-05-29 的数据：

sql_tables <- glue("
SELECT *
FROM mytable
WHERE timestamp = '2019-05-29'
LIMIT 4
")
table <- dbGetQuery(con, stri_encode(sql_tables, to = "UTF-8")) %>%
     as.data.frame()

但它给我带来了一个错误：

Error in select(conn@ptr, statement) :
  DB::Exception: Key expression contains comparison between inconvertible types: DateTime and String inside timestamp = '2019-05-29'

我该怎么做？我怎样才能摆脱 sql 查询中时间戳列中的小时数？期望的结果是：

ID      value                    timestamp
1       message sent      2019-05-29
2       sold out          2019-05-29

Answer 1

来自manuals data types for date：

A date. Stored in two bytes as the number of days since 1970-01-01 (unsigned). Allows storing values from just after the beginning of the Unix Epoch to the upper threshold defined by a constant at the compilation stage (currently, this is until the year 2106, but the final fully-supported year is 2105).

The date value is stored without the time zone.

所以我们需要将"2019-05-29"日期转换为数字：

as.numeric(as.Date("2019-05-29"))
# [1] 18045

#Origin is same as clickhouse, test:
as.Date(18045, origin = "1970-01-01")
# [1] "2019-05-29"

现在我们可以将其用作数字（未测试）：

SELECT *
FROM mytable
WHERE timestamp = 18045
LIMIT 4

Answer 2

截止日期（时间戳）

SELECT * 从我的表 WHERE toDate（时间戳）='2019-05-29' 限制 4
SELECT * 从我的表 WHERE timestamp => toDateTime('2019-05-29') and timestamp < (toDateTime('2019-05-29') + interval 1 day) 限制 4

SQL 查询以获取时间戳列中没有小时数的数据

SQL query to get data without hours in timestamp column

sql

r

clickhouse